The present invention relates generally to fasteners for joining wood pieces, and more particularly to an improved fastener that securely locks into place within a pair of joined wood pieces to substantially prevent undesired shifting or separation of the joined wood pieces, such as, for example, in securing components of a wooden picture frame.
Conventional fasteners for joining a number of wood pieces are typically made from metal and may contain a substantially planar section having portions that enter each of the number of wood pieces to prevent the wood pieces from separating from one another. The ends of the wood pieces may be positioned relative to one another to form various types of joints (miter joints, for example). Some existing metal fasteners, such as V-nails, are folded at portions along their planar section to improve their strength and stability during driving.
To further improve the strength and stability of a joint, prior art metal fasteners may include one or more corrugations. These corrugations may be angled with respect to ends of the metal fastener to draw the wood pieces together as they are joined, reducing separation of the wood pieces.
U.S. Pat. No. 4,514,126 to Knowles discloses a corrugated staple having first and second pairs of angled corrugations extending the full height of the staple, from a trailing edge to a leading edge. A third pair of corrugations runs parallel to the trailing edge and leading edge. Notches on the sides of the staple facilitate handling and shipment of the staple.
U.S. Pat. No. 2,156,682 to Dimoush discloses a metal fastener having a sheet-like metal body formed of flat or curvilinear, transverse corrugations extending from an upper driving edge to a lower sharpened, serrated entering edge. Grooves within the corrugations contain lateral projections to help secure the joint formed by the wood pieces and the metal fastener.
U.S. Pat. No. 2,377,169 to Mohr discloses a corrugated metal fastener having a number of vertically spaced barbs projecting outwardly from each end and from an apex of the corrugations. The triangle-shaped barbs project upwardly (towards the driving edge) and outwardly for biting into wood pieces after the corrugated metal fastener has been driven.
While these and other prior art metal fasteners help increase maintenance of a joint, they do not sufficiently address the problem of inadvertent shifting of the metal fastener within the wood pieces to be joined, particularly when the ends of the pieces are joined at an angle to one another (such as with a miter joint). If the wood pieces are shifted (during transport, for example), or if the wood flexes (due to shrinking, expanding, warping, for example) the metal fastener has a tendency to loosen from within the wood. This in turn loosens the joint, causing additional shifting of the wood pieces, which adds to the problem. Also, the prior art fasteners may damage the wood fibers to a greater extent than the present invention as they are driven into the wood pieces.
Accordingly, one object of the present invention is to provide an improved fastener that is less likely to undesirably shift from within a joint than prior art fasteners.
A further object of the present invention is to provide an improved fastener that is easy to manufacture.
A still further object of the present invention is to provide an improved fastener that enables tighter locking than previous fasteners, yet is not substantially more difficult to drive and minimizes damage to wood fibers.
Yet another object of the present invention is to provide an improved fastener that is dimensioned substantially similarly to typical fasteners, to allow a wide variety of applications.
These and other objects are met or exceeded by providing an improved fastener for joining at least two wood pieces, the fastener having a plate-like member defined between a leading edge and a trailing edge. The leading edge is configured to enter the wood pieces before the trailing edge. In one principal type of embodiment, the fastener also includes at least two corrugations formed on the plate-like member, extending in a generally longitudinal direction, and a locking portion disposed on the plate-like member near the trailing edge for locking the fastener within the wood pieces. A longitudinal direction is defined as the direction extending from the leading edge toward the trailing edge.
By providing this locking portion near the trailing edge, or drive end, of the plate-like member, the fastener can be driven substantially as easily as with prior art devices. However, after the corrugations have drawn the wood pieces together, and as the trailing edge is driven into the wood pieces to be joined, the locking portion is compressed by the wood pieces. This locks the wood pieces while they are tightly drawn together, thus locking the fastener within the joint, and more securely holding the wood pieces together, even during shifting or flexing of the wood pieces.
The locking portion preferably includes one or more rows of projections such as, but not limited to, barbs and dimpled projections. If more than one row of projections is utilized, the projections may be staggered among the rows. The corrugations may be straight or angled with respect to sides of the plate-like member.
An alternate locking portion includes a non-corrugated section near the trailing edge, defined by trailing outer ends of corrugations that extend from the leading edge towards the trailing edge, but terminate longitudinally short of the trailing edge so that an area is created for the non-corrugated section longitudinally between the trailing outer ends of the corrugations and the trailing edge. This enables the wood pieces to compress around the non-corrugated section and the trailing outer ends of the corrugations, to further secure the fastener. The non-corrugated section may contain barbs and/or dimpled projections, and these may be arranged in rows and/or staggered.
Instead of a plate-like member typical with a corrugated nail, the present invention also contemplates a fastener such as an improved V-nail having a folded rectangular section and a locking portion. In addition, the V-nail may include one or more corrugations similar to that of a corrugated fastener, and the corrugations may extend longitudinally to the trailing edge or terminate short of the trailing edge to create a non-corrugated portion.